import java.util.HashSet;
import java.util.Scanner;

/**
 * @author gao
 * @date 2025/6/4 16:22
 */

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String str = scanner.nextLine();
        scanner.close();
        HashSet<Character> hs = new HashSet<>();
        char[] chars = str.toCharArray();
        for (char c : chars) {
            hs.add(c);
        }
        for (char c : hs) {
            System.out.print(c);
        }
    }
}